Various types of microphones and receivers have been used through the years. In these devices, different electrical components are housed together within a housing or assembly. For example, a microphone may include a micro-electromechanical system (MEMS) device with a diaphragm, and integrated circuits, among other components and these components are disposed within the housing. Other types of acoustic devices may include other types of components. These devices may be used in hearing instruments such as hearing aids or in other electronic devices such as cellular phones and computers.
Microphones typically use a diaphragm and the diaphragm is often placed in the vicinity of an electrical conductive plate. As is known, as sound pressure moves the diaphragm, the conductive plate's charge is thereby varied to responsively produce an electric current and this current represents the sound energy. The area between the diaphragm and the plate is a high electric field area (e.g., approximately 11V/3 micro meters or approximately 4*106 V/m or 40 kV/cm).
Venting holes are often formed through the diaphragm. These venting holes serve various purposes. In one example, the venting holes are environmental vents that provide for pressure equalization for the device.
Although the venting holes on the diaphragm offer some advantages, the holes also create a pathway for particles and condensable vapor to enter the high field area from the exterior of the microphone. If the particles or vapor are successful in entering this high field area, then the device may not operate properly.
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